How to Find Your Perfect Kozii One Piece Size

Finding the right swimsuit size can feel harder than it should.

Your usual dress size is a useful starting point, but it isn't the best way to choose a one piece. Torso length, fabric, style and how you plan to swim all affect how a suit feels on your body.

Kozii suits are designed to fit firmly and stay comfortably in place in the water. If you're used to fashion swimwear, your Kozii may feel a little firmer when you first try it on. That's intentional; it's designed for swimming, not standing still.

Here's how to find the right size, and what to do if you're between sizes.

Start with your measurements, not your dress size

Australian dress sizing isn't standardised between brands, so a size 12 in one label won't necessarily fit like a size 12 in another.

That's why we recommend measuring yourself and working from the Kozii size chart.

Take your measurements over your underwear rather than over clothes, and keep the tape snug without pulling it tight.

• Bust — around the fullest part

• Underbust — directly beneath the bust, snug

• Waist — around your natural waist

• Hips — around the fullest part of your hips

• Torso — from the top of your shoulder, down the front of your body, between your legs and back up to the same shoulder point

Your measurements give you a much more reliable starting point than the number on your jeans.

Don't forget your torso

Torso length is one of the most important — and most overlooked — measurements when choosing a one piece.

Two women can have almost identical bust, waist and hip measurements but need different sizes because their bodies are different lengths from shoulder to crotch.

A one piece that's too short through the torso can pull down on the shoulders, feel restrictive and make the whole suit feel too small, even when the width is right.

If you're long in the body, you may need to size up to give yourself the extra length you need. That's not because you're bigger — it's because the garment needs more length.

If you're shorter through the torso, excess length can create extra fabric or wrinkling through the front.

This is why we always recommend checking your torso measurement alongside your bust, waist and hip measurements.

How should a Kozii swimsuit feel?

Kozii suits are designed to feel firm and supportive when dry, without digging in or restricting your movement.

You should be able to:

• Move your arms freely overhead

• Bend and twist comfortably

• Sit down without the suit pulling uncomfortably

• Move through your full swimming stroke

• Wear the suit without constantly adjusting the straps or leg line

Swim fabric relaxes slightly in water, so a suit that feels supportive and close when dry should become more comfortable once you're swimming.

The goal isn't to feel squeezed into your swimsuit. The goal is to feel secure enough to forget you're wearing it.

Fabric can change the fit

Kozii uses several fabrics, and they don't all behave exactly the same way.

Chlorine Tough (CT)

Our Italian Chlorine Tough polyester is designed specifically for chlorinated pools. It's a firmer, less forgiving fabric than our recycled nylon and has less stretch.

If you already know your Kozii size in another fabric, consider going up one size in CT.

Recycled nylon

Our recycled nylon has more stretch and recovery, allowing it to mould more readily to the body.

If you're familiar with our recycled nylon suits, you'll notice that CT feels firmer in comparison.

Thermals

Thermal swimwear is different again. The fleece backing takes up some of the internal volume, so the fit can feel closer than the same size in a standard suit.

If you've purchased Kozii before, your previous size and fabric are useful information when choosing your next suit.

Style can change how a suit feels

Different Kozii styles distribute support differently, so think about where you like to feel the most support.

Elite Bind - Our bound racerback with wide-set straps. It's designed to feel particularly secure and locked in, especially through the shoulders and back.

Xover - Crossed straps give a little more flexibility through the shoulder and make the suit easier for some people to get on and off.

Shelf Support - Features a built-in support layer and can be a good option if you're a D cup or above and prefer more support through the bust.

Full Coverage - Provides more coverage through the back and leg without changing the underlying Kozii fit standard.

If you're choosing between styles, think less about the label and more about how you want the suit to feel when you're swimming.

What if I'm between two sizes?

This is one of the questions we get most often.

Our general advice is simple:

If you're genuinely between two sizes, choose the larger size.

But don't automatically size up if your measurements sit comfortably within one size.

A suit that's too large can be just as uncomfortable as one that's too small. It may move around in the water, gape at the leg or back, or require constant adjustment.

So:

Measure first. Size up if you're genuinely on the line.

And remember that fabric matters. If you're choosing Chlorine Tough and already know your size in another Kozii fabric, consider going up one size.

Still not sure? Ask us

You don't have to work it out on your own.

We make our suits ourselves in Tweed Heads, so we know how each fabric and style fits and how they behave in the water.

Send us your:

• Bust

• Underbust

• Waist

• Hip

• Torso measurements

And tell us what you'll be using your suit for — pool laps, ocean swimming, squad, diving, or simply getting in the water with the kids.

We'll tell you what we'd choose.

We'd rather spend five minutes helping you get the right size than have you swimming in a suit that doesn't feel right

And if you'd like some extra reassurance when ordering, Australian customers can add returns cover at checkout for $3.50.

Find Your Size →

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Frequently Asked Questions

Do Kozii swimsuits run small?

Kozii suits are designed to fit firmly rather than small. They may feel more supportive and closer to the body than fashion swimwear, particularly when dry. That's intentional — they're designed to stay comfortably in place while you swim.

Should I size up in Kozii?

If your measurements genuinely sit between two sizes, we recommend choosing the larger size. If your measurements fall clearly within one size, choose that size rather than automatically sizing up.

If you're choosing Chlorine Tough (CT) and already know your Kozii size in another fabric, consider going up one size because CT is a firmer fabric with less stretch.

How do I measure my torso for a one piece?

Measure from the top of your shoulder, down the front of your body, between your legs and back up to the same point on your shoulder.

Keep the tape snug but don't pull it tight.

If you're long in the body, you may need to size up to give yourself the extra torso length.

How tight should a swimsuit be?

A Kozii swimsuit should feel firm, supportive and secure when dry, without digging in or restricting movement.

You should be able to move your arms overhead, bend and twist comfortably, and move through a full swimming stroke without the suit shifting.

It should feel secure — not uncomfortable.

Will my swimsuit stretch out?

A well-made swimsuit may settle slightly during its first few wears, but it shouldn't continue stretching out.

The fabric should retain its shape and recovery when properly cared for. If a suit continues to grow significantly with wear, it may be too large or the fabric may not have enough recovery.

What if I order the wrong size?

Get in touch and we'll help you sort out a return or exchange.

Our Delivery & Returns page has the full details, and you can also contact us with your measurements if you're unsure before ordering.

We're always happy to help you get it right.